These are critical questions for the nation as Congress debates the biggest immigration overhaul since the 1980s. They affect not only the estimated 11 million unauthorized immigrants in the United States, whose chances for citizenship might be directly linked to the issue, but also Americans who believe no reform effort will succeed if the nation cannot fully protect its perimeters.

The questions are hardly new, but that is because they have been tough to resolve for decades now. Legislators, law enforcers and advocates on numerous sides of the immigration issue disagree about whether security along the U.S.-Mexico border is adequate after a decade of staffing and equipment buildup.

Last week, a bipartisan group of eight senators unveiled their framework for comprehensive immigration reform, with the most contentious element being the citizenship-safe borders pairing.

If the senators’ plan becomes law, it would grant probationary status to unauthorized immigrants who meet certain conditions but not allow them to apply for a green card — and ultimately naturalization — until a special commission is created to determine if and when the border is sufficiently fortified.

President Barack Obama also announced an immigration outline last week. It calls for increased border security but does not tie any enforcement benchmarks to the legalization process.

Since 2002, the U.S. government has pumped major resources into patrolling its border with Mexico. The ranks of Border Patrol agents have more than doubled — to about 21,000. The Department of Homeland Security has put up more than 650 miles of pedestrian and vehicle fencing.

The agency also has a fleet of 10 drones for surveillance and high-tech gadgets such as infrared cameras and ground sensors.

In the same time span, the Border Patrol has seen the number of apprehensions drop from a peak of nearly 1.2 million in 2005 to a low of roughly 340,000 in 2011. The count rose slightly last year to nearly 365,000, according to newly released figures.

In the past month, several groups have published studies on border security. Their conclusions differ widely, from showing how the government has spent more on immigration enforcement than all other federal policing efforts combined to finding that border security is lagging or that resources are being used poorly.

“(The border) is more secure than it has been in decades,” said Maureen Meyer, a senior associate on Mexico for the Washington Office on Latin America, a human-rights organization. “I think there has been a huge use of resources on the border, and you are seeing that in the decrease of apprehensions and the number of people crossing.”

Meyer credits the implementation of several border-security measures that Congress has approved in recent years, such as stiffer penalties for unauthorized border-crossers, greater oversight of certain areas of the border and increased personnel and technology.

She said the pressing question should be: How can the government take what is already in place and make it even more effective?

For instance, Meyer recommends that instead of hiring additional Border Patrol agents, the Department of Homeland Security should redirect some existing resources to ports of entry, where people routinely try to enter with false documents or hide in vehicle compartments.